Complementary metal oxide semiconductor (CMOS) imaging sensors are often powered by an energy source having limited power. As a result, power consumption can be an important consideration for extending the performance and/or lifetime of these sensor systems. Most CMOS imaging sensors having high sensitivity and dynamic range consume>50 mW, which may be unsuitable for wireless applications. Some low-power imaging sensors are known. These sensors can consume low amounts of power, in some cases<10 μW. However, even low-power sensors that are used to continuously send images may still result in systems that draw unacceptable amounts of power. For instance, the wireless signal transmission of images from CMOS imaging sensors consumes significant amounts of power due to the large bandwidth of image signals. Another way to reduce the bandwidth can be to generate image signals by monitoring temporal changes or contrast changes. But, generating image signals based on temporal changes or contrast changes may cause the sensor to respond to environmental conditions, such as change of illumination or background movement, in addition to actual target objects.